The invention relates to a heat dissipation device, in particular, to an open-type heat dissipation device having centrifugal blades and having no outer frames.
As an electrical element increases its operation speed, a large amount of heat energy is generated. For a small-size electrical device (e.g. a notebook) having a large number of electrical elements, heat dissipation efficiency directly influences the performance of the electrical device.
Referring to FIG. 1, a heat dissipation fan 10 includes a rotor 11 having a plurality of axial-flow blades, a stator 12, and an outer frame 13. Both the rotor 11 and the stator 12 are located within the outer frame 13. The rotor 11 has axial-flow blades and is driven to rotate by the stator 12.
The axial-flow heat dissipation fan 10 has drawbacks, which are described in the following.
First, to mount the heat dissipation fan 10, a predetermined space corresponding to the size of the outer frame 13 has to be provided within the electrical device. This is disadvantageous to small electrical devices. Flexibility in arrangement of the heat dissipation fan 10 is also restricted.
Referring to FIG. 2A, the arrangement of the axial-flow heat dissipation fan 10 and the electrical elements 20 creates a large system impedance and a poor heat dissipation effect because the air-flow from the axial-flow heat dissipation fan 10 is immediately blocked by the electrical elements 20.
Referring to FIG. 2B, which shows the arrangement of the axial-flow heat dissipation fan 10, and the electrical elements 20, the system impedance is small. However, to contain the axial-flow heat dissipation fan 10, additional space is needed for the electrical device due to the height of the axial-flow heat dissipation fan 10.
Furthermore, the axial-flow heat dissipation fan 10 is not suitable for a high impedance operation. Common electrical devices tend to be small in size, and the density of electrical elements mounted therein is thus increased. Air-flow impedance increases with the increasing density of the electrical elements of the electrical device. Thus, when using the axial-flow heat dissipation fan 10, the heat dissipation effect is poor.
In order to eliminate the above drawbacks of heat dissipation in an electrical device, a centrifugal fan that provides a large amount of air pressure is often used instead of an axial-flow fan. An example of this is the centrifugal fan disclosed in U.S. Pat. No. 5,912,802, in which a blower and heat dissipation fins are placed close to the electrical devices to improve the heat dissipation effect. However, this does not eliminate the drawbacks illustrated in FIG. 2B.
It is therefore an object of the invention to provide a heat dissipation device having centrifugal blades and occupying a small space.
Another object of the invention is to provide a heat dissipation device having centrifugal blades in order to broaden the usage and flexibility in mounting the device.
A further object of the invention is to provide a heat dissipation device having centrifugal blades in order to produce a large amount of air pressure, which is advantageous to the heat dissipation effect of the electrical device.
A final object of the invention is to provide a heat dissipation device having centrifugal blades in order to simplify the structure and the assembly of the heat dissipation device and thereby lower manufacturing costs.
To achieve the above objectives, the heat dissipation device in accordance with the invention includes a rotor, a plurality of centrifugal blades around the rotor, a stator inside the rotor for driving the rotor to rotate, and a base under the rotor and the stator without enclosing the rotor. The base includes a central portion connected with the stator, and a plurality of extension portions extending from the central portion outward. Away from the central portion, a plurality of holes is formed on each of the plurality of extension portions, respectively.
The heat dissipation device can be used in conjunction with various heat dissipation elements such as the heat dissipation fins mounted above the electrical elements in the electrical device, or heat pipes that can transfer heat energy. Therefore, the heat dissipation effect can be improved.
Furthermore, compared with the conventional axial-flow blades, the centrifugal blades in this invention create a larger air-flow resistance thereby producing a better heat dissipation effect.
Moreover, due to the open-type structure and lack of any outer frame, the heat dissipation device is small and allows flexibility in mounting and usage.
In addition, the structure of the base allows the heat dissipation device to be stably mounted in the electrical device while the manufacturing costs are lowered, as the amount of material wasted is minimal.